• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.263-263
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• 2016

최근 반도체 시장에서는 저비용으로 고성능 박막 트랜지스터(TFT)를 제작하기 위한 다양한 기술들이 연구되고 있다. 먼저, 재료적인 측면에서는 비정질 상태에서도 높은 이동도와 가시광선 영역에서 투명한 특성을 가지는 산화물 반도체가 기존의 비정질 실리콘이나 저온 폴리실리콘을 대체하여 차세대 디스플레이의 구동소자용 재료로 많은 주목받고 있다. 또한, 공정적인 측면에서는 기존의 진공장비를 이용하는 PVD나 CVD가 아닌 대기압 상태에서 이루어지는 용액 공정이 저비용 및 대면적화에 유리하고 프리커서의 제조와 박막의 증착이 간단하다는 장점을 가지기 때문에 활발한 연구가 이루어지고 있다. 특히 산화물 반도체 중에서도 indium-gallium-zinc oxide (IGZO)는 비교적 뛰어난 이동도와 안정성을 나타내기 때문에 많은 연구가 진행되고 있지만, 산화물 반도체 기반의 박막 트랜지스터가 가지는 문제점 중의 하나인 문턱전압의 불안정성으로 인하여 상용화에 어려움을 겪고 있다. 따라서, 본 연구에서는 기존의 산화물 반도체의 불안정한 문턱전압의 문제점을 해결하기 위해 마이크로웨이브 열처리를 적용하였다. 또한, 기존의 IGZO에서 suppressor 역할을 하는 값비싼 갈륨(Ga) 대신, 저렴한 지르코늄(Zr)과 하프늄(Hf)을 각각 적용시켜 용액 공정 기반의 Zr-In-Zn-O (ZIZO) 및 Hf-In-Zn-O (HIZO) TFT를 제작하여 시간에 따른 문턱 전압의 변화를 비교 및 분석하였다. TFT 소자는 p-Si 위에 습식산화를 통하여 100 nm 두께의 $SiO_2$가 열적으로 성장된 기판 위에 제작되었다. 표준 RCA 세정을 진행하여 표면의 오염 및 자연 산화막을 제거한 후, Ga, Zr, Hf 각각 suppressor로 사용한 IGZO, ZIZO, HIZO 프리커서를 이용하여 박막을 형성시켰다. 그 후 소스/드레인 전극 형성을 위해 e-beam evaporator를 이용하여 Ti/Al을 5/120 nm의 두께로 증착하였다. 마지막으로, 후속 열처리로써 마이크로웨이브와 퍼니스 열처리를 진행하였다. 그 결과, 기존의 퍼니스 열처리와 비교하여 마이크로웨이브 열처리된 IGZO, ZIZO 및 HIZO 박막 트랜지스터는 모두 뛰어난 안정성을 나타냄을 확인하였다. 결론적으로, 본 연구에서 제안된 마이크로웨이브 열처리된 용액공정 기반의 ZIZO와 HIZO 박막 트랜지스터는 추후 디스플레이 산업에서 IGZO 박막 트랜지스터를 대체할 수 있는 저비용 고성능 트랜지스터로 적용될 것으로 기대된다.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.89-89
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• 2009

높은 소수반송자 수명(life-time)을 가지는 고품위 실리콘 기판은 고효율 실리콘 이종접합 태양전지 제작을 위한 중요 요소 기술 중 하나이다. 본 연구에서는 n-type c-Si 기판을 이용한 고효율 실리콘 이종접합 태양전지제작을 위해 hot water oxidation(HWO) 공정을 이용하여 고품위 실리콘 기판을 제작하였다. 실리콘 기판의 특성 분석은 Qusi-steady state photoconductance (QSSPC)를 이용하여 소수반송자 수명을 측정하였으며, 기판의 면저항 및 wetting angle을 측정하여 공정에 따른 특성변화를 분석하였다. Saw damage etching 된 기판을 웨이퍼 표면으로부터 particle, 금속 불순물, 유기물 등의 오염을 제거하기 위해 $60{\sim}85^{\circ}C$로 가열된 Ammonia수, 과산화수소수($NH_4OH/H_2O_2/H_2O$), 염산 과산화수소수($HCL/H_2O_2/H_2O$) 및 실온 희석불산(DHF) 중에 기판을 각각 10분 정도씩 침적하여, 각각의 약액 처리 후에 매회 10분 정도씩 순수(DI water)에서 rinse하여 RCA 세정을 진행한 후 HWO 공정을 통해 기판 표면에 얇은 산화막 을 형성시켜 패시베이션 해주었다. HF를 이용하여 자연산화막을 제거시 HWO 공정을 거친 기판은 매끄러운 표면과 패시베이션 영향으로 기판의 소수 반송자 수명이 증가하며, 태양전지 제작시 접촉저항을 감소시켜 효율을 증가 시킬수 있다. HWO 공정은 반응조 안의 DI water 온도와 반응 시간에 따라 life-time을 측정하여 진행하였으며, 이후 PE-CVD법으로 증착된 a-Si:H layer 및 투명전도 산화막, 금속전극을 증착하여 실리콘 이종접합 태양전지를 제작하였다.

• Tribology and Lubricants
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• v.35 no.1
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• pp.9-15
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• 2019

Graphene is a fascinating material for fabricating flexible and transparent devices owing to its thickness and mechanical properties. To utilize graphene as a core material for devices, the transfer process of graphene is an inevitable step. The transfer process can be classified into wet and dry methods depending on the surrounding environment. The adhesion between graphene and a target substrate determines the success or failure of the transfer process. As the surface energy of graphene is an important parameter that provides adhesion, it is useful to estimate the surface energy to understand the mechanisms of the transfer process. However, the exact surface energy of graphene is still disputed because the wetting transparency of graphene depends on the polarity of the liquid and target substrate. Previously reported results use graphene transferred by the wet method. However, there are few reports on the surface energy of graphene transferred by the dry method. In this study, the surface energy of graphene transferred by the wet and dry methods is estimated. Wetting transparency occurs for certain combinations of liquids and substrates. For graphene on a polar substrate, the surface energy decreases by 25 and 35% for the wet and dry transfer methods, respectively. However, the surface energy of graphene on dispersive substrates decreases by ~10% regardless of the transfer method. In conclusion, the surface energy of graphene is $36{\sim}38mJ/m^2$, and differs depending on the transfer method and polarity of the substrate.

• Journal of the Korean earth science society
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• v.44 no.6
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• pp.578-593
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• 2023

Intense convective activity and heavy precipitation inundated Seoul and its metropolitan area on July 15, 2017. This study investigated the synoptic-scale meteorological drivers of cold cloud genesis of this event. The WRF-Chem (Weather Research and Forecasting model coupled with Chemistry) model was employed to explore the intricate interplay between meteorological factors and the indirect effects of PM_2.5 aerosols originating from eastern China. The PM_2.5 aerosols' indirect effect was quantified by contrasting outcomes between the comprehensive Aerosol Radiation Interaction experiment (encompassing aerosol radiation feedback, cloud chemistry processes, and wet scavenging in the WRF-Chem model) and ACR (Aerosol Cloud Radiation interaction) experiment. The ACR experiment specifically excluded aerosol radiation feedback while incorporating only cloud chemistry processes and wet scavenging. Results indicated that in the early hours of July 15, 2017, a convergence of warm, moisture-laden airflow originating from southeast China and the East China Sea unfolded over the Yellow Sea. This convergence was driven by the juxtaposition of a low-pressure system over the Chinese mainland and Northwest Pacific high. Notably, at approximately 12 km altitude, the resultant convective clouds were characterized by the presence of ice crystals, a hallmark of continental-origin cold clouds. The WRF-Chem model simulations elucidated the role of PM_2.5 aerosols from eastern China, attributing 5.7, 10.4, and 10.8% to cloud water, ice crystal column, and liquid water column formation, respectively, within the developing cold clouds. Thus, this study presented a meteorological mechanism elucidating the formation of deep convective clouds over the Yellow Sea and the indirect effects of PM_2.5 aerosols originating from eastern China.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.131.1-131.1
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• 2010

This study was conducted for engineering optimization for the gasification process which is the key factor for success of Taean IGCC gasification plant which has been driven forward under the government support in order to expand to supply new and renewable energy and diminish the burden of the responsibility for the reduction of the green house gas emission. The gasification process consists of coal milling and drying, pressurization and feeding, gasification, quenching and HP syngas cooling, slag removal system, dry flyash removal system, wet scrubbing system, and primary water treatment system. The configuration optimization is essential for the high efficiency and the cost saving. For this purpose, it was designed to have syngas cooler to recover the sensible heat as much as possible from the hot syngas produced from the gasifier which is the dry-feeding and entrained bed slagging type and also applied with the oxygen combustion and the first stage cylindrical upward gas flow. The pressure condition inside of the gasifier is around 40~45Mpg and the temperature condition is up to $1500{\sim}1700^{\circ}C$. It was designed for about 70% out of fly ash to be drained out throughout the quenching water in the bottom part of the gasifier as a type of molten slag flowing down on the membrane wall and finally become a byproduct over the slag removal system. The flyash removal system to capture solid particulates is applied with HPHT ceramic candle filter to stand up against the high pressure and temperature. When it comes to the residual tiny particles after the flyash removal system, wet scurbbing system is applied to finally clean up the solids. The washed-up syngas through the wet scrubber will keep around $130{\sim}135^{\circ}C$, 40~42Mpg and 250 ppmv of hydrochloric acid(HCl) and hydrofluoric acid(HF) at maximum and it is turned over to the gas treatment system for removing toxic gases out of the syngas to comply with the conditions requested from the gas turbine. The result of this study will be utilized to the detailed engineering, procurement and manufacturing of equipments, and construction for the Taean IGCC plant and furthermore it is the baseline technology applicable for the poly-generation such as coal gasification(SNG) and liquefaction(CTL) to reinforce national energy security and create new business models.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.661-673
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• 2007

Rock materials of the three-storied stone pagoda in the Cheongryongsa temple in Korea are mainly composed of gneissose two-mica granite and fine-grained granite. This stone pagoda shows structural instability due to cracks and breaking-out of the stones. The surface properties of the stone is highly degraded by various inorganic pollutants and epilithic biospecies. Therefore, this study carried out comprehensive deterioration diagnosis by non-destructive methods, and some conservation treatments base on the diagnosis were carried out to reduce weathering progress. As the treatments, the biospecies and lichen that covering on the stone surfaces were removed by dry and wet cleaning, and degraded concrete applied to the pagoda for restoration in the past was removed and repaired with epoxy resin. Oxidized iron plates inserted between the rock properties were also substituted titanium stainless steels. After all processes are completed, we sprayed consolidant on the rock surface. Finally, the ground of the stone pagoda was rearranged using small rock aggregates, and the fence was established for control of artificial deterioration by visitors and environmental maintenance.

• Journal of the Semiconductor & Display Technology
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• v.4 no.4 s.13
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• pp.19-26
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• 2005

The process optimization of ozone concentration and half life time was investigated in ultra pure water and alkaline solutions for the wet cleaning of silicon wafer surface at room temperature. In the ultra pure water,. the maximum concentration (35 ppm) of ozone was measured at oxygen flow rate of 3 liters/min and ozone generator power over 60%. The half life time of ozone increased at lower power of ozone generator. Additive gases such as $N_2$ and $CO_2$ were added to increase the concentration and half life time of ozone. Although the maximum ozone concentration was higher with the addition of $N_2$ gas, a longer half life time was observed with the addition of $CO_2$. When $NH_4OH$ of 0.05 or 0.10 vol% was added in DI water, the pH of the solution was around 10. The addition of ozone resulted in the half life time less than 1 min. In order to maintain high pH and ozone concentration, ozone was continuously supplied in 0.05 vol% ammonia solutions. 3 ppm of ozone was dissolved in ammonia solutions. The static contact angle of silicon wafer surface became hydrophilic. The particle removal was possible alkaline ozone solutions. The organic contamination can be removed by ozonated ultra pure water and then alkaline solution containing ozone can remove the particles on silicon surface at room temperature.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.399-404
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• 2021

From 1 January 2020, the limit for Sulphur in fuel oil used on board ships operating outside designated emission control areas will be reduced to 0.5 %. This regulation by international maritime organization (IMO) is able to significantly reduce the amount of Sulphur oxides (SOx) discharging from ships and should have environmental advantages and health for all over the world. To meet the regulation, in these days, wet scrubber system is being actively developed. However, this process leads to make washing wastewater. In this study, we evaluated ion exchange resin system in accordance with scrubber wastewater discharge regulation by IMO. Theoretical wastewater used as feed solution of lab scale water treatment systems. The results revealed that nitrate ion was removed selectively in spite of high TDS wash wastewater solution depending on ion exchange resin property. Moreover, it was possible to improve efficiency of the system by optimizing operating conditions.

• Journal of the Korean earth science society
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• v.45 no.1
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• pp.1-18
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• 2024

This study analyzed the effect of warming on PM_2.5 aerosol production in mid-latitude East Asia during June 2020 using PM_2.5 aerosol anomalies, which were identified by incorporating meteorological and climate data into the Weather Research Forecasting model coupled with Chemistry (WRF-Chem) model. The decadal temperature change trend over a 30-year period (1991-2020) in East Asia showed that recent warming has been greater in summer than in winter. Summer warming in East Asia generated low and high pressure in the lower and upper troposphere, respectively, over China. The boundary between the lower tropospheric low and upper tropospheric high pressure sloped along the terrain from the Tibetan Plateau to Korea. The eastern China, Yellow Sea, and Korean regions experienced a convergence of warm and humid southwesterly airflows originating from the East China Sea with the development of a northwesterly Pacific high pressure. In June 2020, the highest temperatures were observed since 1973 in Korea. Meanwhile, enhanced warming in East Asia increased the production of PM_2.5 aerosols that travelled long distances from eastern China to Korea. PM_2.5 anomalies, which were derived solely by inputting meteorological and climatic data (1991-2020) into the WRF-Chem model and excluding emission variations, showed a positive distribution extending from eastern China to South Korea across the Yellow Sea as well as over the Pacific Northwest. Thus, the contribution of warming to PM_2.5 aerosols in East Asia during June 2020 was more than 50%. In particular, PM_2.5 aerosols were transported from eastern China to Korea through the Yellow Sea, where the warm and humid southwesterly airflows implied wet scavenging of sulfate but promoted nitrate production.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.8
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• pp.449-455
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• 2017

Process input data including material and energy, process output data including product, co-product and its environmental emissions of the reference and target processes were collected and analyzed to evaluate the process performance. Environmentally problematic input/environmental emissions of the manufacturing processes were identified using these data. Significant process inputs contributing to each of the environmental emissions were identified using multiple regression analysis between the process inputs and environmental emissions. Optimum combination of the end-of-pipe technologies for treating the environmental emissions considering economic aspects was made using the linear programming technique. The cement manufacturing processes in Korea and the EU producing same type of cement were chosen for the case study. Environmentally problematic input/environmental emissions of the domestic cement manufacturing processes include coal, dust, and $SO_x$. Multiple regression analysis among the process inputs and environmental emissions revealed that $CO_2$ emission was influenced most by coal, followed by the input raw materials and gypsum. $SO_x$ emission was influenced by coal, and dust emission by gypsum followed by raw material. Optimization of the end-of-pipe technologies treating dust showed that a combination of 100% of the electro precipitator and 2.4% of the fiber filter gives the lowest cost. The $SO_x$ case showed that a combination of 100% of the dry addition process and 25.88% of the wet scrubber gives the lowest cost. Salient feature of this research is that it proposed a method for identifying environmentally problematic input/environmental emissions of the manufacturing processes, in particular, cement manufacturing process. Another feature is that it showed a method for selecting the optimum combination of the end-of-pipe treatment technologies.